1. Field of the Invention
The present invention relates to well bore cleaning assemblies and more particularly to clean out assemblies for cleaning well casing perforations by water pressure.
2. Description of the Prior Art
In my prior U.S. Pat. No. 4,892,145, issued on Jan. 9, 1990, I have described a new, mechanical, clean out tool for opening well perforations in a well casing. This tool is particularly useful in fracturing solid debris collected and blocking the casing perforation.
In the course of pumping well fluids from any ground formation silt, sand, and other particulate matter migrate to the well bore and then deposit at the perforations in the casing. Eventually this accumulation closes off the flow and the well becomes unproductive. Thus periodic cleanout is necessary and, depending on the form and chemistry of the accumulate, this cleanout may require mechanical or water flow mechanisms, or both.
One mechanical arrangement has been referred to above and reference is therefore invited to the teaching of my prior U.S. Patent for the manner of operation of such a device. Water based cleanout devices in the prior art typically take the form of a manifolded mandrel tied to the end of a hollow rod string through which water, at pressure, is conveyed into the well bore. To confine this water pressure to the mandrel length, an upper and lower resilient thimble seal are provided.
These prior devices, while suitable for the purposes intended, occasionally hang up and are opposed in their passage by offset partings in the casing, occasional collapse in the casing walls, or bends or dog legs in the bore.
Thus a water cleaning assembly that passes these occasional defects is extensively sought and it is one such assembly that is disclosed herein.